Railway signaling system



c. VLEG. FORTESCUE.

RAILWAY SIGNALING SYSTEM. APPLICATION mso AUG.28, 1915. RENEWED NOV. 5,I920.

1,396,825. Patented Nov. 15, 1921. v

WITNESSES v INVENTOR I Y [/mr/es Z96. fZr/esme BY UNITED STATES PATENTOFFICE.

CHARLES LE G. 'FORT'ESCUE, CF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TOWEST- INGHOUSE ELECTRIC AN'D MANUFACTURING COMPANY, A CORPORATION OF.rmmsnvama Specification of Letters Patent.

Patented Nov. 15, 1921.

Application filed August 28, 1915, Serial No. 47,884. Renewed November5, 1920. Serial No. 422,078.

To all whom it may con/0mm:

Be it known that I, CHARLES LE G. Fonrnsoos, a subject of the King ofGreat Britain, and a resident of Pittsburgh, in the county of Alleghenyand State of Pennsylvania, have invented a new and useful Improvement inRailway Signaling Systems, of which the following is a specification.

My invention relates to systems of electrical distribution, and it hasspecial reference to alternating-current railway systems embodying meansfor minimizing inductive disturbances in adjacent electrical circuitsand, at the same time, offering paths for the unimpeded flow in thetrack circuits of the alternating currents adapted to operate thesignalingdevices that afford protection to the railway systems.

In electrical-railway systems operated by alternating currents, meansare usually provided for minimizing the inductive disturbances arisingfrom the flow of the propulsion currents. At the same time, thesignaling currents must be confined to their re- SPBCtlVGblOCk sectionsor track circuits in order to properly operate the signaling devicesaifording protection to the traffic accommodated by the railway. One ofthe most effective means for minimizing the inductive disturbancesarising from the propulsion currents contemplates the insertion of anumber of series transformers at spaced intervals in the railway system,the primary windings of the transformers being connected in seriescircuit relationship with the trolley or third rail conductor, and thesecondary windings thereof being connected, preferably through impedancebonds, to the track rails and in shunt to the insulating joints. Thissystem for minimizing inductive interferences is fully described inUnited States PatentNo. 1,196,300 issued to Chas. F. Scott, Aug. 29,1916, for means for minimizing inductive interference. By inductivelyinterlinking the track circuit and the trolley conductor, as mentionedabove, electromotive forces are impressed at intervals in the railswhich serve to confine the flow of the propulsion currents to them. Inconjunction with the above system, means must be provided for permittingthe unimpeded flow of the signaling currents in each of the blocksections or track circuits.

An object of my invention, therefore, is

to provide a novel means for dividing the track into block sections ortrack circuits for signaling purposes without breaking the electricalconductivity of the rails for the return flow of the propulsioncurrents. In conjunction therewith, means are incorpo rated forinductively interlinking the trolley and the rails with each other inorder to confine the return flow of the trolley currents to the latterso as to minimize the inductive interferences that may be impressed uponan adjacent electrical circuit, such as an intelligence transmissioncircuit.

In addition to accomplishing the aforementioned object, my presentinvention permits series transformers such as are shown in theaforementioned United States Patent No. 1,196,300, and employed forimpressing compensating electromotive forces at intervals in the trackrails to more perfectly interlink the same with the trolley or supplyconductor, to be inserted in circuit at oints intermediate the ends ofthe signaling locksections or track circuits without impeding the flowof the signaling currents in the separate block-sections of the track.Ordinarily, the signaling currents would be impeded since the insulatingjoints in the rails necessary for connecting these series transformersin circuit would offer high impedance to the flow of thesignalingcurrents. By means of my invention, however, the series transformers maybe connected in circuit at frequent intervals and intermediate the endsof the signaling block sections and other insulated track sectionswithout impairing the electrical conductivity of the rails as regardsthe flow of the propulsion currents and the flow of the signalingcurrents in the block-sections.

My invention is particularly adapted to be employed in connection with arailway sys tem comprising a plurality of tracks each of which has anassociated trolley or power supply conductor, and in which theblocksections of one track are staggered and maintained electricallyindependent with respect to the block-sections of another paralleltrack. To provide suitable paths for the power currents, the severaltracks are electrically interconnected in parallel relationship so as toconstitute a conductor of low impedance for the return flow of the powercurrents. The series transformers, therefore, are common to all of theadjacent tracks, the secondary windings of said transformers'beingrequired to conductthe power currents flowing in the several tracks. thesame time, the signaling block-sections are maintained electricallvindependent of one another, although portions of the transformerwindings are common paths for both the powercurrents and the signalingcurrents. By means of my present invention, the aforementioned resultsmay be obtained, andthe series transformers adapted for accomplishingthem may be economically constructed by providing a plurality of pathsthrough the transformer windings for the high value power currentsflowing therethrough. V

Other advantages accruing from the use ofmy invention will behereinafter described and pointed out with particularity in the appendedclaims.

For a better'understanding of the nature and scope of my invention,reference may be had to the following description and to theaccompanying drawing, the single figure of which is a diagrammaticrepresentation of a railway system embodying a form of my invention.

A source of. power or propulsion current (not shown) is connected totrolley conductors 1 and 2, and to their associated tracks 3 and 4,respectively, in the usual manner. The tracks comprise paths for thereturn flow of these propulsion currents. Spaced insulating joints 5 areinserted at intervals in the trolley conductors 1 and 2, and, similarly,spaced insulating joints 6 and 7 are inserted in the tracks 3 and 4. Incertain instances, additional insulating joints 8 and 9 are inserted inthe tracks in order to divide them into a series of insulated blocksections or track circuits each of which is protected by means of asignaling device 10. For the purpose of illustration only, one signalingdevice 10 is shown associated with each of the tracks 3 and 4, but itwill be understood that these signaling devices are disposed atconvenient intervals along the railroad, depending upon the character ofthe protection to be afforded.

Adjacent to each other and on each side of the insulating joints 8 and 9are inserted impedancebonds 11, and adjacent to the insulating joints 6and 7 are inserted other impedance bonds 12, each of said impedancebonds comprising current-carrying windings provided with taps at theirmid-points. An intelligence transmission conductor 8 shown as atelephone conductor, is disposed adjacent to the trolley conductors 1and 2 and the tracks 3 and t and is, therefore, under the inductiveinfluences arising from thecurrents flowing over the aforementionedrailway circuits. It is important,

therefore, to minimize the inductive disturbances impressed upon thetelephone conductor S in order to insure the satisfactory transmissionof intelligence. At the same time, means must be provided for the effective operation of the signaling devices 10 in order that the traiiicaccommodated upon the several tracks may be amply protected. To thisend, transformers 13 and it have been provided each of which comprises aplurality of windings that are connected in circuit with the tracks, aswill be hereinafter described.

Since the two railway systems are substantially similar, my descriptionwill be confined to that one comprising the trolley conductor 2 and thetrack 1 it being understood that the operation of the other railwaysystem is identical therewith. It will be noted that a block section ortrack circuit 15 is formed in the track at by means of the spacedinsulating joints 8* and 9 which are inserted in the rails of the track.The several block sections comprising the railway system are connectedtogether through impedance bonds 11, in order to constitute a continuouspath for the flow of the propulsion currents as hcreinbefore described.Intermediate the insulating joints 8 and 9 which form the block section15, I

have disposed the insulating joints 6 and 7 which are spaced from oneanother, as will be hereinafter described, in order that the insulatingjoint 5 in the trolley 2 may be disposed substantially midway betweenthem. On the sides of the insulating joints 6 and 7 adjacent to theinsulating joints 8 and 9, I have disposed the impedance bonds 12, themid-points of which are connected through conductors 16 and 17 tocorresponding mid-points of the impedance bonds 12 inserted in the trackAt the same time, the conductors 16 and 17 are connected to theterminals of secondary windings 18 and 19 of the transformer 13. ings 20and'21, which are connected across the insulating joints 5 in thetrolley conductors 1 and 2, respectively, serve to inductively interlinkthe several trolley conductors with their associated tracks. In thismanner, the return flow of the trolley currents is confined to thetracks, the relative flow over the tracks 3 and 4 being adjustable bymeans of taps 22 provided on the secondary windings 18 and 19.Consequently, in the illustrated system, the propulsion currents aresubstantially equal ized in all four of the rails, by reason of theprovision of the four equal-impedance paths including the respectivehalves of the impedance bonds 12. Since the return flow of thepropulsion currents is confined to the tracks 3 and 4, the inductivedisturbances that may be impressed upon the transmission conductor 8 aresubstantially Primary windnegligible. This condition of operation andresult are in accordance with the systems shown and described in theaforementioned United States Patent, No. 1,196,300.

However, provision must be made for the operation of the signalingdevices 10 and, to this end, the insulating joints 6 and 7 arerespectively shunted by windings 23' and 24 of the transformer 13. Whenthe rails comprising the block section 15 are not bridged by a train,the signaling currents which are supplied from a power supply circuit 25through a transformer 26 flow over a circuit comprising a rail-section27, a conductor 27, the inductive current carrying winding 23 of thetransformer 13, a conductor 27", a lead 28, a signaling relay 29, a lead30, a rail section 31, a conductor 31, the current-carrying inductivewinding 24: of the transformer 13, a conductor 31". and the secondary ofthe transformer 26. As the current flows through the signaling relay 29,the signal 10 controlled thereby operates to indicate safety. It will benoted that the signaling currents traverse the current-carrying windings23 and 2 .1 simultaneously and in opposite directions and, consequently,the inductive effects arising therefrom are substantially neutralized,thereby providing a path of negligible impedance for the flow of thesignaling currents.

When a railway train indicated at 32 bridges the rail sections 27 and31, the signaling currents are shunted through the trucks of the railwaytrain, thereby shortcircuiting the sign ttl relay 29 which operates thesignals to indicate danger. It will be noted that the impedance bonds 11confine the signaling currents to the insulated block section 15 andthat these currents are also shunted across the insulating joints 6 and7 by the inductively related windings 23 and 24 of the transformer 13.

It will be observed that the two tracks 3 and 4: are electricallyinterconnected through the impedance bonds 1.2 and the common conductors16 and 17 leading to the secondary windings 18 and 19 of the transformer13. Because of the inductive relation between these secondary windingsand the secondary windings 23 and 24 with their associated primarywindings 20 and 21, the propulsion currents of both railway systems areconfined to the paths afforded by the aforesaid secondary windings. As aconsequence thereof, the windings 23 and 2a of the transformer 1.3 areso designed as to carry both the signaling currents and a portion of thereturn propulsion currents, sin e the pro ulsion currents, which are ofrelatively high values, are divided between the windings 23 and 2-1.connected in shunt to the insulating joints 6 and 7 respectively, andused as paths for the flowof the signaling currents, and the secondarywindings l8 and 19.

The current-carrying windings of the transformer 13 serving to interlinkthe trolley conductors and the tracks with one anotherare wound upon asingle iron core, thereby closely inductively interlinking the severalwindings with one another. The whole is then inclosed in a single casingto comprise one transformer, such as shown at To provide for theadjustment of the currents flowing through the respective(-urrent-carrying windings, taps are provided as is usual for regulatingpurposes.

In actual installations, it has been found that, under certainconditions of separation of the rail insulating joints and theirposition in the track with respect to the insulating joints in thetrolley conductor, a large portion of the propulsion currents may beforced through the signaling relay, sometimes in sufficient quantity toburn it out. The solution of this trouble is dependent upon thedimensions of the locomotive and may be solved by setting a limitationof a certain number of feet, namely, 5 feet. be tween the insulatingjoints 6 and 7 in the two rail sections 27 and 31, respectively, andhaving the insulating joint 5 in the trolley conductor 2 disposedsubstantially midway between the said insulating joints in the track.This requirement is based on the dimensions of the locomotive 32 toinsure that both. of the track joints 6 and 7 are bridged. by thelocomotive before the insu- I lating joint 5 in the trolley conductor 2is crossed by the pantograph shoe 33 of the locomotive.

While the foregoing description has been confined to the operation ofthe track ft, by referring to the signaling block-section of the track3,it will be noticed that the windings of the transformer 14 areconnected to the track 3 in a manner similar to the connection ofcorresponding windings of the transformer 13 to the track 4.

It will be apparent that each of the transformers interlink both tracks3 and 4t and the trolley conductors 5 with one another. Again, the blocksections are continuous to the flow of the signaling currents, althoughthe rail sections are broken. by insulating joints that are employed inconnection with the series-transformers 13 and 14-. By employing thesecondary windings 18., 19, 23 and 24, the propulsion currents aredivided therebetween, thereby eliminating the necessity of furnishing asingle winding which would, of necessity, comprise a conductor of verylarge cross-sectional area in order to permit the propulsion currents ofthe several railway systems to flow therethrough. At the same time, twoof the secondary windings, namely, 23 and 24, are employed to conductsignaling currents around the insulating joints 6 and 7 insertedintermediate the ends of the block sections.

By employing my invention, a single transformer suffices to inductivelyinterlink both the tracks and their associated power conductors. Inaddition, means are employed for rendering the separate block sectionselectrically continuous for the signaling currents, although said blocksections are interrupted by insulating joints. By providing a pluralityof secondary windings, such as herein described, as a substitute for asingle winding comprising a conductor of large cross-sectional area, aneconomical construction of the transformers may be effected.

While I have shown one embodiment of my invention, it will be understoodby those skilled in the art that many modifications may be madethereinwithout departing from the spirit and scope of the appended claims.

I claim as my invention:

1; In a railway system, the combination with a source of propulsioncurrent supply, a trolley conductor connected thereto, a source ofsignaling current, a track comprising a plurality of insulated sections,said track forming a portion of a signaling circuit, and additionalinsulating joints inserted in the rails comprising each of saidsections, of means for inductively interlinking the track andthe trolleyconductor in order to confine the return flow of the propulsion currentto the track and to permit unimpeded flow of a signaling current in eachinsulated section.

2. In a railway system, the combination with a source of propulsioncurrent supply, a trolley conductor connected thereto, a source ofsignaling current, a track comprising a plurality of insulated sections,and additional insulating joints inserted in the rails comprising eachof said sections, of means for inductively interlinking the trolleyconductor and the track in. order to confine the return flow of thepropulsion current to the track and means for inductively interlinkingthe rails of each section in order to provide a substantially unimpededflow for the signaling current in each of said sections.

3. In a railway system, the combination with a source of propulsioncurrent supply, a trolley conductor connected thereto, a source ofsignaling current, a track comprising a plurality of insulated sections,and additional insulating joints inserted in the rails comprising eachof said sections, of primary windings connected in series with thetrolley conductor, secondary windings inductively related therewithconnected in shunt to said insulating joints in order that thepropulsion-current flow may be confined to the track, andcurrent-carrying windings also connected in shunt to said insulatingjoints, said last named windings being inductively related with eachothe' and with said primary windings to provide unimpeded paths for theflow of signaling currents in the block sections and paths for the flowof the propulsion currents.

4. The combination with two railway tems each having a track and atrolley Con ductor, a source of propulsion current supply therefor, asource of signaling current, insulating joints inserted in the rails ofthe tracks, and impedance bonds adjacent to said insulating joints forconnecting together the rails of each track, of spaced transformershaving primary windings connected in series circuit with the trolleyconductors and a secondary winding connected in common to the impedancebonds inserted in both tracks, and windings inductively related to eachother and to said primary windings, said inductively related windingsbeing connected in shunt to said insulating joints of one track toprovide an unimpeded path for the simultaneous flow therethrough ofsignaling currents and portions of the propulsion current.

5. The combination with a plurality of railway systems each having atrack and a trolley conductor, a source of propulsion current supplytherefor, a source of signaling current, and insulating joints insertedin the trolley conductors and the rails of the tracks, of transformershaving primary windings connected in shunt to the insulating joints ofthe trolley conductors, and secondary windings connected in shunt to theinsulating joints in the rails for interconnecting all the trackstogether, and other secondary windings so inductively interlinking therails of one track that substantially unimpeded paths for the flow ofsignaling currents are provided.

6. In an electric railway system employing alternating current both forpropulsion and signaling, the combination of a track consisting of tworails, a third conductor paralleling said track, means whereby saidthird conductor may be made to serve as one side, and the two rails inparallel as the other side of said propulsion circuit, means wherebysaid track may be made to serve as the circuit of said signalingcurrent, a series transformer having one winding in series with saidthird conductor and the other winding in series with the other side ofsaid propulsion circuit, and means whereby said series transformer maybe effectively connected to Said propulsion circuit at any point in asignal section without rendering said signal section discontinuous forsignaling currents.

7. In an electrical transmission system for the simultaneoustransmission of two separate component alternating currents, thecombination of three parallel conductors, two of which seriallyconstitute the circuit ing alternating current of one of said componentcurrents and in parallel one side of the circuit of the other of saidcomponent currents; an insulating joint in each of said two conductors;means associated with said two conductors whereby said first namedcomponent current is transmitted across said insulating joints,

and a second means connected in series with the third conductor andmutually inductively related with said first-mentioned means, wherebythe current in said third conductor and the sum of the currents in saidtwo conductors in parallel may be substantially equalized. l a

8. In an electric railway system employing alternating current for bothpropulsion and signaling, the combination of a track consisting of twocondurting rails; means whereby said rails serially constitute thecircuit of said signaling current and in parallel one side of thecircuit of said propul sion current; a third conductor paralleling saidtrack; an insulating joint in each of a said two rails of said track;means whereb said si nalin current ma be transb l i mitted across saidinsulating joints; and a second means connected in series with saidthird conductor and mutually inductively related with said first namedmeans, whereby said propulsion current in returning to its source may beconfined entirely to the rails associated with said third conductor.

9. In an electrical transmission system for the simultaneoustransmission of two separate component alternating currents, thecombination of three parallel conductors, two of which seriallyconstitute the circuit of one of said component currents and in parallelone side of the circuit of the other of said component current aninsulating joint in each of said two conductors and the third conductor;and a transformer having a primary winding bridgingthe insulating jointin said third conductor and a pair of secondary windings bridging theinsulating joints of said two conductors, respectively,

so as to offer a substantially unimpeded path across said insulatingjoints for the ffow of u the first-mentioried component current. i l l10. In an electric railway system cmployfor both propulsion andsignaling, the combination of a track consisting ottwo conducting rails;means whereby saidrails serially constitute the oil.- cuit of saidsignaling current and in parallel one side of the circuit of saidpropelsion current, a third conductor paralleling said track; aninsulating joint in each of said rails and in said third conductor; anda transformer having a primarywinding bridging the insulating joint insaid third conductorand a pair of secondary windin bridgingtheinsulating joints of said rail s respectivelymoas to 0 er asubstantially unimpeded path across said insulating joints for the flowof signaling current in opposite directions in said rails.

11. in an electrical transmission system, the combination of two pairsof conductors adapted for the simultaneous transmission of two; separatecomponent alternating cur rents, the two conductors of each pairserially constituting the circuit of one of said coi'nponcnt currentsand in parallel one side of the circuit of the other of said componentcurrents, an insulating joint inserted in each of said. conductors, apair of mutually inductive windings associated with the conductors oione of said pairs so as to offer a substantially unimpeded path acrosssaid insu lating joints for the flow of the first of said cinnponentcurrents in opposite directions in the two conductors, and means forequal.- izing the flow of the second of said component currents in thesame direction across said insulating joints in all four conductors.

12. A system as specified in claim 11, said mutually inductive windingsbridging the insulating means of their associated'conduetors. j

13, In an alternating-current railway signaling system of the typewherein thetwo rails of? each track serve as parallel paths for thereturn flow of propulsion currents and also as the two sides of thesignaling current circuits, the combination of a pair of tracks, eachcomprising a pair of rails, insulating joints inserted at correspondingpoints in each of said tracks, a pair of mutually inductive windings,associated with the rails of one track so as to offer a substantiallyunimpeded path across said insulating joints tor the flow of signalingcurrents in opposite directions in the two rails, and means forequalizing the flow of propulsion currents in the same direction acrosssaid in sulating-joints in all four rails, and for preventing harmfulground currents.

14:. A system as specified in claim 13, said mutually inductive windingsbridging the insulating joints of their associated rails.

15. 111 an electrical transmission system employing two separatecomponent alternating currents, the combination of a plurality of groupsof conductors, each group com the conductors of all of said groups; atransformerhaving primary windings connected across the joints ofthethird conductors of the respective groups, and a pair of secondarywindings bridging the insulating by rendering said conductors joints ofsaid two conductors of one of said groups so as to offer a substantiallyunimpeded path across. said insulating joints for the flow of the firstof said component currents in opposite directions in said twoconductors; and means for equalizing the flow of the second of saidcomponent currents in the same direction across said insulating jointsin said two conductors of all of said groups.

16. In an electric railway system employing alternating current for bothpropulsion and signaling, the combination of a plurality of tracks, eachcomprising a pair of rails; means whereby the two rails of each trackserially constitute the circuit of the respective signaling currents andin parallel one side of the circuit of the propulsion current; a trolleyconductor for each track; insulating joints-inserted at correspondingpoints in each ofsaid rails and trolley conductors; a transformer havingprimary windings connected across the joints of the respective trolleyconductors, and a pair of secondary windings bridging the rail joints ofone of said tracks so as to offer a substantially unimpeded path acrosssaid insulating joints for the flow of signaling currents in oppositedirections in said rails, and means for equalizing the flow ofpropulsion currents in the same direction across said insulating jointsin all of the rails, and for preventing harmful ground currents.

17. In an electrical transmission system, the combination of a pluralityof groups of conductors, each group comprising three parallelconductors, adapted for the simultaneous transmission of two separatecomponent alternating currents, two of which conductors seriallyconstitute'the circuit of one of said component currents and in parallelone side of the circuit of the other of said, component currents,insulating means inserted in each of said two conductors atcorresponding points in each group, therediscontinuous means associatedwith said two conductors in one of said groups whereby the first of saidcomponent currents may be transmitted across said point ofdiscontinuity, and transforming means associated with saidthirdconductors and said two oonductorsin parallelin each group, wherebythe sum of the currents in said third conductors and the sum of thecurrents in said two conductors in both groups in parallel may besubstantia 11y. equalized.

"=18. In-an electric railway system employing alternating current forboth propulsion and signaling, the combination of a pluralityof'itracks, each of said tracks consisting of two conducting rails;means whereby the two rails of'each track serially constitute thecircuit-of the respective signaling currents 'andin parallel Joneside'of the circuit 01" said propulsion current; a plurality of thirdconductors paralleling sald plurality of tracks: an insulating joint ineach rail of said plurality of tracks; means associated with one of saidplurality of tracks whereby the naling current associated with saidtrack may be transmitted across said insulating joints; and a secondmeans associated with said third conductors and said rails in each trackwhereby said propulsion current associated with said plurality of tracksin returning to its source may be confined entirely to said plurality oftracks.

19.,In an electrical transmission system. the combination of two pairsof parallel conductors; insulating joints inserted at correspondingpoints in each of said conductors, whereby said conductors are di videdinto parallel sections, the parallel sections of each pair being adaptedfor the simultaneous transmission of two separate component alternatingcurrents, the two sections of each pair serially constituting' thecircuit of one of said component currents and in parallel one side ofthe circuit of the other of said component currents: an inductancedevice disposed at each side of the insulating joints of one of saidpairs of conductors and having its terminals connected to the respectivesections of said pair, each of said inductance devices being providedwith a mid-tap; a transformer having three windings, one of saidwindings bridging said mid-taps, the other two windings bridging theinsulating joints in the respective conductors of the other pair; andmeans connected to said transformer for equalizing the second componentcurrents in the conductors ofsaid other pair and for equalizing also thesecond component currents in the two pairs, whereby all four conductorsare used to carry the second component currents required by a load oneither pair of con-- ductors.

20. In an alternating-current railway signaling system of the typewherein the two rails of each track serve as parallel paths for thereturn flow of propulsion currents and alsoas the two sides of thesignaling current circuits, the combination of a pair oi tracks. eachcomprising a pair of rails; an insulating joint in each of said rails; asource of alternating currents for signaling, a signal controllingdevice, and an inductance device all connected across the rails of oneof said tracks on each side of said insulating joints, each of saidinductance devices being provided with a mid-tap; a transformer havingthree windings, one of said windings bridging said mid-taps, the othertwo 7 bridging the insulating joints in the respective rails of theother track; and means connected to said transformer for equalizing thepropulsion currents in the rails of said other track and forequalizing-also the propulsion windings currents in the two tracks,whereby all four rails are used to carry the propulsion currents forvehicles on either track.

21. The system as specified in claim 19, including two additionalwindings on the transformer, a. third conductor for each of said pairsof conductors, and insulating joints in each of said thirdconductors,said additional transformer windings being connected acrossthe insulating joints of the respective third conductors.

22. A system as specified in claim 20, including two additional windingson the transformer, a trolley conductor for each track, and aninsulating joint in each of said trolley conductors, said additionaltrans former windings being connected across the insulating joints ofthe respective trolley conductors.

23. In an electrical transmission system, the combination of two pairsof conductors adapted for the simultaneous transmission of two separatecomponent alternating currents, the two conductors of each pair seriallyconstituting the circuit of one of said component currents and inparallel one side of the circuit of the other of said componentcurrents, an insulating joint inserted in each of said conductors, aninductance device connecting the conductors of each pair on each side ofsaid insulating joints, each of said inductance devices beingqprovidedwith a mid-tap, a pair of connecting devices, one of said connectingdevices connecting the mid-taps of the two inductance devices which areconnected to the respective pairs of conductors on each side of saidinsulating joints, and a transformer having three windings, two of saidwindings being connected respectively across the insulating joints oi.

the conductors of one of said pairs, and the remaining winding havingits respective terminals connected to said connecting means. i U H 24'.an alternatingmurrent railway s1g-,

naling system, the combination of a pair of tracks, each comprising apair of rails, an insulating joint in each of said rails, an in ductancedevice connecting the rails of each track on each side of saidinsulating joints, each of said inductance devices, being provided witha mid-tap, a pair of connecting conductors, one of said connectingconductors connecting the mid-taps of the two inductance devices whichare connected to the respective track-rails on each side of saidinsulating joints, and a transformer having three windings, two of saidwindings being connected respectively across the insulating joints ofthe'rails of one of said tracks, and. the remaining winding having itsrespective terminals: connected to said connecting conductors.

25. The system as specified in claim 23, including two additionalwindings on th tcm for preventing the flow of earth-currents and forproviding the use of an alternatingcurrent block signaling system, thecombination of a pair of tracks, each comprising a pair of rails; atrolley conductor for each of said tracks; means whereby said trolleyconductors may be made to serve as one side and the four rails inparallel as the other side of the circuit for propulsion currents; meanswhereby the two rails of each track may be made to serve as the twosides of the circuit for signaling currents; and means for inductivelyinterlinking said tracks and trolley conductors in such a manner as toconfine the return flow of the propulsion current to the track, topermit substantially unimpeded flow ofsignaling currents in one sectionof said tracks, and to impede the flow of signaling currents in theadjacent sections of track.

28. A system as specified in claim 10. characterized, by the fact thatthe joints in the runs. are disposed at points not exactly opiosite toeach other, but close enough togethcr so that both rail joints will bebridged by the wheels of a passing vehicle before the third-conductorjoint is bridged by the current-collecting device of the vehicle,whereby the signalingcircuit is protected against abnorn'lal voltages.

29. In an alternating-current railway sys tem 'for preventing the flowof earth currents and for providing for the use of analternating-current block signaling system, the combination of aplurality of tracks comprising two pairs of rails; a trolley conductor;means whereby said trolley conductor may be made to serve as one sideand the four rails parallel as the other side of the circuit forpropulsion currents; an insulating joint in each of said rails and insaid trolley conductor; a source of alternating currents for signaling,a signal controlling device, and an inductance device all connected fromone rail to the other on each side of said insulating joints, each ofsaid inductance devices being provided with a mid-tap; a transformerhaving one winding connected across the insulating joint of said trolleyconductor, and another winding having its terininals connected to saidmid-taps, the joints in the rails being disposed at points not exactlyopposite to each other but close enough together so that both railjoints will be bridged bythe wheels of a passing vehicle before thetrolley-conductor joint is bridged by the currentcollecting device ofthe vehicle, whereby the signaling circuit isprotected against abnormalvoltages.

' 30. In an 'electric'railway system employing alternating current forboth propulsion and signaling-the combination of a track consisting oftwo conducting rails; means whereby said rails serially constitute thecircuit of said signaling current and in parallel one side of thecircuit of said propulsion current a third conductor paralleling saidtrack; an insulating joint'in each of said two rails of said track andin said third conductor; transforming means bridging said insulatingjoint in said conductor and said insulating joints in said rails in sucha manner as not to short circuit said signaling current, whereby saidpropulsion current in returning to its source may be confined entirelyto the rails associated with said third conductor, the joints in therails being disposed at points not exactly opposite to each other, butclose enough together so that both rail joints will be bridged by thewheels of a passing vehicle before the third-conductor joint is bridgedby the current-collecting device of the vehicle, whereby the signalingcircuit is protected against abnormal volt- -e 31. In analternating-current railway signaling system, the combination of a pairof tracks, each comprising a pair of rails, an insulating joint in eachof said rails, an inductance device connecting the rails of each trackoneach side ofsaid insulating joints, each of said inductance devicesbeing provided with a mid-tap, connecting means connected with saidmid-taps for equalizing the propulsion currentsin all four of saidrails,'a trolley conductor for each of said tracks, means'in series withsaid trolley conductors and mutually inductively related to saidconnecting means whereby the sum of the currents in said trolleyconductors and the sum of the currents in said rails may besubstantially equalized, means whereby the rails of the respectivetracks may serve as the circuits for alternating signaling currents,characterized by the fact that the joints in the rails of each track aredisposed at points not exactly opposite to each other but close enoughtogether so that both rail joints will be bridged by the wheels of apassing vehicle before the corresponding trolley conductor joint isbridged by the currentcollecting device of the vehicle, whereby thesignaling circuits are protected against abnormal voltages.

A system as specified in claim 16, characterized by the fact that thejoints in the rails of each track are disposed at points not exactlyopposite to each other but close enough together so that both railjoints will be bridged by the wheels of a passing vehicle before thecorresponding trolley conductor joint is bridged by thecurrent-collecting device of the vehicle, whereby the signaling circuitsare protected against abnormal voltages.

33. A system as specified in'claim 22, characterized by the fact thatthe joints in the rails of each track are disposed at points not Xactlyopposite to each other but close enough together so that both railjoints will be bridged by the wheels of a passing vehicle before thecorresponding trolley conductor joint is bridged by thecurrent-collecting device of the vehicle, whereby the signaling circuitsare protected against abnormal voltages.

34-. A system as specified in claim 27, characterized by the fact thatthe joints in the rails of each track are disposed at points not exactlyopposite to each other but close enough together so that both railjoints will be bridged by the wheels of a passing vehicle before thecorresponding trolley conductor joint is bridged by thecurrent-collecting device of the vehicle, whereby the signaling circuitsare protected against abnormal voltages.

In testimony whereof, I have hereunto subscribed my name this 19th dayof Aug, 1915.

CHARLES LE Gr. FORTESCUE.

